PETER Weis, chief engineer at Polar Tank Trailer, said vapor-recovery systems on chemical tanks are not required by code, but they are installed on an estimated 50% of new tanks at the request of the purchaser, or else provisions are added for later installation.
He said the reasons for installing them on tanks or retrofitting the tanks come out of the Truck Trailer Manufacturers Association's (TTMA) Technical Bulletin #123, which was released May 18, 2007. “Vapor Recovery Retrofit of MC 307 and MC 312 Cargo Tanks” provides guidelines for the retrofit of vapor recovery equipment on existing chemical and acid cargo tanks.
To comply with the Environmental Protection Agency's (EPA) rule, “National Emission Standards for Hazardous Air Pollutants: Organic Liquids Distribution (non-Gasoline).”
To control nuisance odors during loading and unloading.
To provide a means of reducing the risk of all accidents by keeping operators off the top of the tank with some systems.
“In researching this, I didn't realize how common these systems are,” Weis said during the 2011 Cargo Tank Maintenance Seminar October 24-26 in Louisville, Kentucky. “I did, and I didn't. I went to our back lot, and it was full of vapor-recovery systems. It's a pretty important consideration.”
He said the use of vapor-recovery systems is promoted by the Cargo Tank Risk Management Committee (CTRMC), which was formed on March 17, 2010, and is made up of leading industry professionals with the sole task of proactively enhancing cargo tank safety.
CTRMC estimates that there are over 250,000 cargo tank motor vehicles in use across North America today, with each one representing at least four to five workers who perform assigned work duties on top of them every day.
CTRMC promotes the use of vapor-recovery systems because they provide uniformity of systems that enhance safety and keep workers off of tanks.
Weis listed the types of vapor-recovery systems, as found in TB 123:
- Minimal system.
It consists of manually operated ball valve and quick coupling in the spilldam area, and requires the operator to access the top of the tank with a hose.
- Piped manual system.
It consists of a ball valve, with a line running to the ground. There's a ground-level connection, but the valve is opened at the top.
- Hydraulic system.
It consists of a hydraulic top valve, with a line running to the ground. There's a ground-level connection with ground-level controls.
For guidance, the following Recommended Practices and Technical Bulletins are available:
TTMA RP 102 (May 2, 2008), “Vapor Recovery Line Configurations for DOT 407 and DOT 412 Cargo Tanks.” Establishes standard configurations for vapor-recovery lines on DOT 407 and DOT 412 cargo tanks. These configurations provide for top (on the tank) and bottom (near the tank outlet) vapor recovery. This RP is not intended to address the retrofit of vapor-recovery systems on existing cargo tanks.
TTMA TB 122 (April 23, 2010), “Operation of Typical Vapor Recovery (VRL) Lines on DOT 407 and DOT 412 Cargo Tanks.” Intended to instruct personnel how to operate typical vapor-recovery lines on DOT 407 and DOT 412 cargo tanks. These lines conform with RP 102.
On September 23, 2011, CTRMC released TB 125, “General Ladders and Tank Access Equipment Maintenance.” It is intended to suggest a general side-access ladder configuration for use on new and used one-compartment cargo tanks with a capacity of approximately 6000 to 8000 gallons, and a top walkway. It also has ladder dimensions that are suitable for retrofitting chemical and food-grade tanks. ♦